1. Field of the Invention
The present invention relates to a voice/voice band data discrimination apparatus for discriminating voice/voice band data or the like, more particularly to an apparatus for discriminating voice data so as to create statistical data and to an apparatus for discriminating voice/voice band data in digital speech interpolation (hereinafter called "DSI") and digital circuit multiplication equipment (hereinafter called "DCME").
2. Description of the Prior Art
As a conventional voice/voice band data discriminating apparatus, there- are known two cases according to the purposes.
FIG. 8 is a block diagram showing a conventional voice/voice band data discrimination apparatus employed in DSI and DCME. This apparatus is designed in such a manner as to catch or identify a tone of 2100 Hz set in the head of a FAX and/or modem signal. Similarly, it is also designed so as to catch a specific frequency for identifying a signaling.
A signal employed in each of the DSI and DCME is represented in the form of a digitized PCM (Pulse Code Modulation) signal of 64 kbps. A judgment as to whether or not the signal is represented in analog or digital form offers no essential problem with respect to the intended functions. However, the digital signal is deeply correlated to the apparatus employed in the DSI and DCME which simultaneously deal with a number of channels. Therefore, a description will be made herein of the digital signal by way of example.
An input signal to be transmitted over a telephone line is supplied to an input terminal 1 and divided into two. One of the two signals is inputted to a signal processing unit 13 for the DSI and DCME, and the other thereof is supplied to a tone discriminator 12. The tone discriminator 12 is comprised of filters or the like and detects a single frequency. When the frequency detected at this time is 2100 Hz, it is determined to be voice band data. In other words, it is judged to be a FAX and/or modem signal. Then, the signal processing unit 13 receives the result of determination or discrimination from the tone discriminator 12 to thereby performing processing based on the contents of discrimination.
FIG. 9 is a block diagram showing another conventional example. This is an apparatus of the type wherein the spectrum for an input signal is analyzed and the contour of the spectrum is determined from the arithmetic operation, as shown in FIG. 10, so as to judge it to be a voice sound when a one-sided low frequency is formed, to judge it to be a modulated wave when a one-sided high frequency is formed, and to judge it to be a tone only when a specific spectrum is represented, whereby the contents of the signal is discriminated.
In this apparatus, the input data measuring circuit 14 measures data necessary for the spectrum analysis based on a signal inputted from a signal input terminal 1. Then, the spectrum for the data is determined by a spectrum analysis/arithmetic circuit 15 provided at the stage after the input data measuring circuit 14. Thereafter, a statistical processing circuit 16 performs necessary statistical calculation.
As an alternative to the apparatus used for the above purpose, there is known one in which the number of zero crosses is used as one element for the judgment of the contents of the signal and employed in combination of the same with other functions.
The conventional voice/voice band data discrimination apparatus is constructed as described above. Since the circuit shown in FIG. 8 detects only a signal of 2100 Hz, the modem signal itself cannot be detected. Therefore, a signal from the apparatus with no tone of 2100 Hz set in the head thereof and a modem signal, which appears after the top or head signal of 2100 Hz has passed therethrough, cannot be detected.
The Fourier arithmetic processing is performed to determine the spectrum for the input signal in the circuit shown in FIG. 9. Therefore, its processing becomes complex and the apparatus is large-sized in structure. In particular, the apparatus employed in the DSI and DCME which simultaneously deal with many channels has problems that it becomes large and its manufacturing cost is high.